The use of steam is extremely widespread and commonplace, with examples including power generation, cooking, ironing clothes, humidity adjustment and even medical treatment, therapeutics (such as steam baths) and so on. As for the conventional methods of supplying steam, the majority rely on a combustible fuel (such as wood, coal, gasoline and natural gas, etc.) or electrical heating, whereby water is first heated. However, regardless of whether a fuel or electrical means of heating water are employed, and although the heat source is in close proximity to the liquid being heated, the heat must travel through a medium (such as a water container or metal heating tubes), which is essentially indirect heating. Therefore, in addition to the shortcomings of poor heating efficiency and the wasting of energy resources, a certain amount of preheating time is required before the water being heated reaches a high temperature and it is therefore virtually impossible to produce steam in a predictable short period of time. In terms of practical usage, such approaches have disadvantages such as wasted time, inconvenience and low efficiency. Furthermore, when a user fails to notice that all the water in the water container has evaporated, and the fuel or electrical power source continues to provide heat, the drawback is not only a waste of energy, but the aforesaid water container, heating tubes and other heating components become damaged or a hazardous situation may result.